Certain passenger services in passenger transport vehicles (such as aircraft, ships, buses, trains, and any other passenger transport vehicles) cause waste water to accrue. This may occur from food service, hand washing, or from showers that may be provided on-board private or luxury aircraft or other vehicles. Waste water from these services is often referred to as grey water, which is “spent” or “used” water that drains from drinking water systems, from wash basins during hand washing, material poured down a galley sink, a shower drain, or any other instance in which water is soiled or loaded with waste (e.g., soaps, detergents, soils from washing). Grey water typically does not include contaminants such as septic wastes (water containing septic waste is generally referred to as “black water”).
Most large passenger transport vehicles are equipped with a grey water system, which can collect and store grey water, as well as waste tanks that collect and store black water for eventual disposal. (In the absence of special valves, such as those described by U.S. Pat. No. 7,533,426 titled “Grey Water Interface Valve Systems and Methods,” health standard guidelines for airlines have required that septic water (“black water”) be vacuumed away separately from grey water because, if a back-up were to occur, sewage would be expelled from galley and lavatory sinks, as well as toilets, which could create a myriad of health problems.) Accordingly, the added expense of keeping grey and black water separate has generally been necessary. However, smaller vehicles may not have a separate grey water tank and may discharge grey water to the atmosphere via a drain mast.
However, if grey water is disposed outside the aircraft, it should be heated because aircraft travel at such high altitudes and where the air is so cold, that discharging grey water at room temperature may cause it to freeze immediately. Accordingly, drain masts may be provided that heat grey water prior to its discharge. This uses extra energy, adds to maintenance issues (e.g., clogs often form and need to be removed), and can cause safety problems on the ground if the drain masts are not turned off (e.g., extremely hot liquids can be discharged from a plane on the ground and scald a worker standing below the plane). Another problem with drain masts is that they create drag against the vehicle skin. This can be a particular concern on an aircraft, where drag can lower fuel efficiency and create higher operation costs.
Additionally, some airports will not allow grey water to be deposited on their tarmacs, causing airlines to find alternate solutions to outside disposal. Depositing wastes outside an aircraft that are contaminated with detergent and other soils can also be an environmental hazard. Additionally, disposing grey water outside the aircraft during travel may cause the material to “paint” the side of the plane, creating a soiled, unsightly streak alongside the body of the aircraft. This adds to maintenance and cleaning costs and could tarnish an airline's reputation for being professional and well-maintained. Accordingly, alternate solutions for disposing or storing of grey water are needed.
Most passenger aircraft have a vacuum disposal system that applies vacuum to transport waste water from toilets and/or sinks into an on-board waste water storage tank. The vacuum is generated either by the pressure differential between the pressurized cabin and the reduced pressure outside of an aircraft at high flight altitudes or by a vacuum generator at ground level or at low flight altitudes.
Currently, many luxury and private aircraft are equipped with showers. These showers can create a large volume of grey water—more than that created from typical galley and lavatory sinks. Galley and lavatory sinks are generally connected to small diameter drain lines (which can easily back up if clogged or if a high flow is introduced) and terminate at the aircraft drain mast for exhaustion to the atmosphere, but disposing of many gallons of shower water can create unsolved problems.
Another concern with moving water through an aircraft (or other vehicle with a vacuum waste system) is that existing vacuum designs can be quite loud. A flushing sound is created when the flush valve opens (e.g., the toilet flush valve). On an aircraft, differential pressure is typically what forcefully draws waste and water material down the drain. (Although on land or on other vehicles, a vacuum generator may be used to generate vacuum.)
Accordingly, it is desirable to provide a flow control unit or system that can manage the transport of grey water within passenger transport vehicles, such as aircraft. It is desirable for such a system to conduct this transport in a discrete, relatively quiet, and environmentally friendly manner. It is also desirable to provide a system and method for storing grey water in the black water (or septic) tanks that are on-board an aircraft.